Google Analytics made it easier for getting rid of a duplicate or test account, now, you can delete an account with a click of a button in the "Edit Account and Data Sharing Settings" page. If you're the administrator of the account, and the account is not linked to any other Analytics or AdWords accounts, deleting your account is easy. (If you want to delete a linked Analytics account, you can contact support.) Also, if you have many account administrators on your account, don't worry - they will receive an email notifying them of the account deletion. But they should let the other non-admin account users know that the account is deleted to avoid any confusion.
Note: Make sure to remove the tracking code from your site after you delete your account. Remember, there's no "undo" once you delete your account, so before you delete your account forever, we'll ask you to confirm that this is really what you want to do before you delete it.